Timing control system



Nov. 2, 1943. c. J. COLLOM 2,333,363

\ TIMING CONTROL SYSTEM Filed Sept. 26, 1940 52 Q l 12w INVENTQR(7:25:15 1 6211017.

BY I

ATTOP a Patented Nov. 2, 1943 3 UNITED STATES PATENT. OFFICE TIMINGCONTROL SYSTEM Cletus J. Collom, Detroit, Mich. Application September26, 1940, Serial No. 358,473

(on. 2so=27 9 Claims.

The present invention relates to timing control systems, and inparticular provides an improved timing control system in which allcontrol functions are performed by valves of the electronic type, asdistinguished from relays of the usual electromagnetic or other type.

It will be appreciated from a complete understanding of the presentinvention that, in a generic sense, the improvements thereof may beembodied in timing systems designed to produce widely varying sequencesand designed for a wide variety of specific purposes. Ina morerestricted sense, the present timing control system has been designedparticularly to control an electric welding machine of theresistancetype, so as to pro vide, without the use of electromagnetic controlrelays, a desired welding sequence.

The principal objects of the present invention are to provide a timingcontrol system of the above indicated character, which is simple inarrangement and which is reliable in operation; to provide such a systemcomprising a plurality of related electronic valves, so arranged as toprovide, without the use of cooperating electromagnetic or othertranslating devices, the hereinafter described operating'sequence; andto generally improve and simplify the construction and arrangement ofelectronic timing systems.

With the above, as well as other and more detailed objects in view,which appear inthe following description and in the appended claims, apreferred but illustrative embodiment of the invention is shown in theaccompanying drawing, in which'the sole figure is a diagrammatic view ofa circuit arrangement embodyingthe-invention.

Referring to the drawing,-the systemcomprises generally a series ofelectronic valves VI V2, V3, V4, V5, V6, V1, V8 and V9, all whereof areof usual construction, characterized asbeingv effective to transmitcurrent in one direction so long as a predetermined potential of properpolarity is applied between the principal electrodes thereof, and solong as the potentials of the grids thereof are at or above apredetermined potential with respect to the associatedcathodes. As willbe understood, however, when the grid potentials fall below thejust-mentioned critical value, or stated-in another way, when aso-called blocking potential is appliedto the grids, the correspondingvalves immediately become non-conducting.

Valves VI, V2, V4, V6, V1 and V9-areillustrated as being of thefour-elementtype, each such valve being provided with a filament, acathode, a grid and-a plate. The just-mentioned elements associated withvalve VI are designated, respectively, f, c, g and p, and it will beunderstood that the corresponding elements for theother four elementvalves are correspondingly arranged. Valve V is provided with the aboveelements, and, in additiomis. provided with an auxiliary or" screengrid. The remaining'two valve v3 and vs are of the three-el menttYbdcompnsrng 9- caithbli, a grid and a plate, whichelerhnts, for'valveV3, are designated, respectively, 0'3, 03 and p3.

Th details or tfi connections between the variousvalves may best beunderstood from a descriptiono'f vthe operation of the system as aWhole". Before proce ding to such a detailed desc rilitioli, hOWVeI,fili following summary Of the operation is given.

The startingof the system is under the contrOl of a pilot Switch o'fstarfiil'ig device 1?, which i ma be of any suitable manual or'automatic ype, but'is' shown b'in'g' amanuan operable push button.closure" or the push button P initiates a s quence of operations, whichcauses t e valve v3 to conduct current and, energize the winding: or anelectromagnetic val e mi The valve I'll is conventionally" arranged (bymeans nots'ho'wn') so that upon energizatiori it applies an or" otherfluid pressure between the welding electrodes l2 and [4, .so as to movethem into clamping" engagement with the'work in readiness for a weldingperation; closure or thejp'ilot switch Palso initiates a furthersequence-or operation's, which at the expiration of a predeter minedtl'm'e aftertlie e'iiergization of the electro magnetic valve" ll),causes the valve V8" to' conduct current. Thelatteractioii' causeswelding current to besli'ppli'd to the e lctrode s', thereby initiatingthe weldirigactidii. ass-hows; valve vs directly energizes" a usualweldihlzijc'ont'a'ctor WC, the contact member a, whereofisfdirectlyjconnecteli in the primary circuit of the welding transformerT. 1

contemporaneously with the e'ner'gization of the welding circuit, timingmeans are actuated which" become" efie nve, at ul'e expiration" of" a;predetermined pence; tojinterrupt the flow of welding current.Thereafter; at the expiration 1 of what-isconventioiially'lrriown as ahold-time", the previouslymentioned electromagnetic valve" I0 is Ide-eh'erg'i'zed, thereby automatically'relievin'g" the pressure betweenthe 'electrode'sf and terminating the cycle;

In the present arrangement; also; timing means are rendered effective asan incident to" the timingaction, to preveirit'ule initiation of asecond welding cycle for' a predetermined" period" after the release" oftheelectrodesalttheconclusion of the j just mentioned first cycle.

ccnsideringnow' the: details orthesystem; the syste'm may be;conditioned for" operation by closing" the usual disconnect switches SIand" S2, which action connects thesuppiy conductors LI and L2 to asuitable sourceof alternating c'urrent. This action immediatelyenergizes thefprimar'y windings of transfc'jrr'x'z'er's' T3, T4, T8, TlI and HT, whichwinding's ara'll directlycoririe'cte'd between the" line"conductors" LI and 132,

as will be obvious. The transformer HT serves to supply heating currentto the filaments or cathodes of all of the valves VI through V9, whichrelation is indicated by the reference character X applied to all suchfilaments or cathodes and to the terminals of the secondary winding ofthe transformer HT. So long as the line con" ductors LI and L2 areenergized, accordingly, the filaments or cathodes of the several valvesremain heated in readiness for operation.

The energization of transformers T3, T1 and TII renders thesetransformers effective to apply alternating potentials between theprincipal electrodes of the associated valves V2, V6 and V9, whichactions are, however, without immediate effect, since, as describedbelow, the corresponding said valves are in a blocked or non-conductingcondition. The energization of transformer T4 applies an alternatingpotential between the principal electrodes of the valve V4, which is nowin a conducting condition, and thereupon passes current to energize theassociated transformers T5 and T6, the primary windings whereof aredirectly connected in the plate circuit of valve V4. The secondarywinding of transformer T5 is connected to the grids of valves V2 and V3,and upon being energized, transformer T5 applies blocking potentials tothe grids of valves V2 and V3, which valves are consequently renderednonconducting'for the time being. The energization of transformer T6applies a corresponding blocking potential to the grid of valve V6,which also thereupon becomes non-conducting for the time being.Transformer T6 also charges a weldingdelay condenser C2, which isincluded in the grid circuit of the valve V6.

The energization of transformer T8, which resulted, as aforesaid, fromthe initial closure of the disconnect switches SI and S2, appliesalternating potential between the principal electrodes of the valve V1,which thereupon conducts cur rent and energies the transformers T9 andTIS. It will be noticed that the, primary windings of transformers T9and T I9 are directly connected in the plate circuit of the valve V1 andupon being energized, transformers T9 and TH! apply blocking potentials,respectively, to the grids of valves V8 and V9. Transformer TI 0 alsocharges the weld-time condenser C3.

Assuming now that it is desired to effect a welding operation, the pilotswitch P may be closed. This action directly energizes the primarywinding of the control transformer TI, the secondary winding whereofthereupon applies alternating potential across the principal electrodesof the valve VI. Under the conditions stated, as aforesaid, the valveV2, which is associated with the grid circuit of valve VI, isnon-conducting, and the grid of valve VI'is, therefore, at a potentialwhich enables valve VI to conduct cur rent. The energization oftransformer TI, therefore, causes valve VI to pass current and energizethe control transformer T2.

The secondary winding of transformer T2 is included in the grid circuitof valve V4, and upon being energized, serves to charge up the holdtimecondenser CI, and to also apply a blocking potential to the grid ofvalve V4. The action of the hold-time condenser CI, and its relatednow-blocked discharge valve V5 are described below.

Upon the application of the just-mentioned blocking potential to thegrid of valve V4, this valve is immediately rendered non-conducting,which action immediately de-energizes the previously mentioned controltransformers T5 and T6.

The de-energization of transformer T5 removes the previously existingblocking potentials from the grids of valves V2 and V3, whereupon thesevalves assume a conducting condition. Upon being rendered conducting,valve V2 passes current, as influenced by the transformer T3, and servesto not only charge up the off-time condenser C4, but to also apply ablocking potential to the grid of the valve VI. The latter actionrenders the valve VI non-conducting, thereby de-energizing thetransformer T2. This action is without effect upon the conductivity ofthe valve V4, however, since the hold-time condenser CI remains fullycharged and will remain so until a discharge circuit is providedtherefor through the valve V5, as hereinafter described.

The removal of the blocking potential from the grid of the valve V3renders the latter conducting. Consequently, valve V3 conducts currentand energizes the winding of the electromagnetic valve it, whichthereupon, as previously described, actuates the electrodes I2 and I4,so as to bring them into clamping engagement with the work.

The de-energization of transformer T6, which also resulted, asaforesaid, from the blocking of valve V4, enables the energy initiallystored in the welding-delay condenser C2 to start discharging throughthe associated resistor R2. At the expiration of a predetermined period,accordingly, determined by the adjustment of the condenser C2, the gridof valve V6 assumes a conducting potential, thereby enabling theinitially energized transformer T1 to cause a flow of current in theplate circuit of the valve V6. The time element provided by thecondenser C2 is preferably sufiicient, as will be appreciated, to insurethat the electromagnetic valve ID will have caused the electrodes tomove into clamping engagement with the work before the flow of weldingcurrent is initiated.

The conductivity of the valve V55 enables the 1 transformer TI to applya blocking potential to the grid of the valve VI, which, as will berecalled, was in a conducting condition at the beginning of theoperations now being described. As a consequence of the just-mentionedaction. valve V'I immediately becomes non-conducting, which actionde-energizes the transformers T3 and'TID.

The secondary winding of transformer T9 is directly connected in serieswith the now deenergized transformer TI2 and with the grid of the valveV8, and upon the de-energization of transformer T9, valve V8 is renderedconducting. Consequently, a circuit is now completed, including theprincipal electrodes of valve V8, for the winding of the Weldingcontactor WC, which thereupon closes its indicated contact members tocomplete the circuit for the welding transformer T. This action, as willbe appreciated, initiates the flow of welding current between thewelding electrodes.

The secondary winding of transformer TIIl is directly connected to thegrid of the valve V9, and upon the de-energization of transformer Till,the energy previously stored thereby in the weld-time condenser C3starts to discharge through the associated resistor R3! At theexpiration of ,a period determined by the charac teristics of condenserC3, the grid of valve V9 assumes a potential at which valve V9 isconducting, enabling the initially energized transformer Tl l to passcurrent between the principal electrodes of valve V9.

The flow of current through the valve V9 energizes transformers TI: andTH, the secondary windings whereof are included in parallel relation inthe grid circuits of valves V8 and V5.

The energization of transformer T12 again applies a blocking potentialto the grid of the valve V8, thereby interrupting the flow of current tothe welding ccntactor WC. Consequently, the welding contactor WC resumesthe illustrated open position, interrupting the flow of current throughwelding transformer T, and terminating the flow of welding current.

As aforesaid, the valve V is provided with an auxiliary or screen grid,which functions to retain valve V5 in a non-conducting condition, exceptwhen transformer Tlfl is energized. The energization of transformer T03,however, which results from the timing out of condenser C3, asaforesaid, immediately applies a potential to the other grid of valveV5, which overcomes the bias of the screen grid, andrenders valve V5conducting.

As aforesaid, the plate circuit of valve V5 is connected in parallelwith the hold-time condenser Cl. Upon being rendered conducting,acoordingly, valve V5 completes a discharge circuit for condenser Cl,through the resistor RF, and

at the expiration of a, predetermined period, sufficient to allow thework to cool sufficiently to cause the weld to set, the grid of valve V4assumes a conducting potential. At this time, valve V4 again becomesconducting, re-energizing trans formers T5 and T5. The re-energizationof transformer T6 again applies a. conducting potential to the grid ofvalve V6 in preparation for the next operation, as described below.

The re-energization of transformer T5 again applies blocking potentialto the grids of valves V2 and V3. The latter action interrupts the flowof current in the plate circuit of valve V3, thereby de-energizing theelectromagnetic valve f0 and relieving the pressure acting against theelectrodes. The blocking of valv V2 interrupts the flow of current inthe plate circuit thereof, thereby enabling the energy initially storedin the oiltime condenser C4 to start discharging through the associatedresistor R4. At the expiration of a predetermined interval determined bythe characteristics of condenser C4, the grid of valve VI assumes aconducting potential, in readiness for the next operation. It will benoticed that valve VI cannot be rendered conducting so as to initiate asucceeding cycle of operation until condenser Cl has timed out and thiscondenser, therefore, serves to determine the length of the periodbetween the end of one complete welding cycle and the beginning of thenext succeeding cycle.

The blocking of valve V5, which results, as aforesaid, from there-energization of transformer T6, at the expiration of the hold-timeperiod, again renders valve V'I conducting, which action, in turn,re-energizes transformers T9 and Till. The re-energization oftransformer T9 is without immediate effect, since under the conditionsstated, the grid of valve V8 is maintained at a blocking potential bythe transformer TIZ.

The re-energization of transformer TI 0 applies a blocking potential toth grid of valv V9, which thereupon becomes non-conducting, deenergizingthe transformers TH and I13, The de-energization of transformer Tl2leaves the grid of valve V8 at a blocking potential under the influenceof transformer T8. The de-energization of transformer Tl; renders theassociated grid of valve V5 ineffective to overcome the biasing effectof the screen grid sg, associated with this valve, enabling the lattergrid to maintain the valve V5 non-conducting.

It will be appreciated that the variou re-setting operations, whichoccur at the conclusion of the hold-time interval, determined by thetiming out of condenser Cl, restore the system to the condition,described above, as existing immediately prior to the closure of thestarting switch P.

If the starting switch P is in the closed position at the time condenserC4 times out, terminating the off-time interval and renderin valve VIconducting again, the consequent energized condition of transformer TIinitiates a new welding' cycle, which duplicates in all respects thepreviously described cycle. If, on the otherhand, the switch P is in theopen position at the time condenser C4 times out, such timing out doesnot initiate a new welding cycle for the reason that the transformer Tiis de-energized. A new welding cycle may, however, b initiated at anytime after the timing out of condenser C4, by closing the switch P, aaforesaid. It will be recalled from the previous description that valveV'l remains conducting for only a very short interval at the beginningof such welding cycle. Consequently, the switch P is required to be heldclosed only during such momentary interval and thereafter may be openedwithout altering in any way the duration of the welding cycle, oraltering in any way the duration of the off-time interval, which isprovided by the condenser Cl.

It will be appreciated that by suitable adjustment of the various timingcondensers and their associated timing circuits that the duration of thesuccessive stages, described above, may be controlled between relativelywide limits, each such stage being adjustable over a range of from a fewcycles of the alternating current source to a number of seconds.

From the foregoing, it will be appreciated that the present inventionprovides an extremely simple and efficient timing control system, andthat various modifications in the form, number and arrangement of partsmay be made Without departing from the spirit and scope of theinvention.

What is claimed is:

1. In a, timing control system, the combination of an electric valvemeans having principal electrodes and a control electrode actuable tocon-- trol the flow of current between said principal electrodes, anauxiliary valve associated with said control electrode, means normallyrendering said auxiliary valve effective to apply a blocking potentialto said control electrode, and timing means operable to first rendersaid auxiliary valve ineflective to apply said blocking potential andfor thereafter applying a blocking potential to said control electrodeindependently of said auxiliary valve.

2. In a timing control system, the combination of an electric valvehaving principal electrodes and a. control electrode actuable to controlcurrent flow between said principal electrodes, a circuitv for saidcontrol electrode including first and second energizable means eitherwhereof is effective when energized to apply a blocking potential tosaid control electrode, and timing means for maintaining both saidenergizable means de-energized for a predetermined period and forthereafter energizing one thereof.

3. In a timing control system, the combination or an electric valvehaving principal electrodes and a control electrode actuable to controlcurrent flow between said principal electrodes, a circuit for saidcontrol electrode including first and second energizable means eitherwhereof is effective when energized to apply a blocking potential tosaid control electrode, means normally rendering one of said energizablemeans energized and the other de-energized, and timing means operable tofirst de-energize said one energizable means and thereafter energize theother energizable means whereby to cause said valve to conduct currentfor a predetermined interval.

4. In a timing control system, first and second electric valves eachhaving principal electrodes and a control electrode, said first valvebeing normally conducting and having its principal electrodes coupled tothe control electrode of said second valve in such relation that whensaid first valve is conducting it maintains said second valve in anon-conducting condition, a starting device actuable betweencircuit-closing and circuit-interrupting conditions, means responsive toactuation of said starting device from one said condition to the otherfor impressing a potential on the control electrode of said first valvewhich renders it non-conducting, means effective after said first valveis rendered non-conducting for passing current between the principalelectrodes of said second valve, and means operated as a consequence ofsaid actuation of said starting device for removing said potential atthe expiration of a controlled period.

5. In a timing control system, first and second electric valves eachhaving principal electrodes anda. control electrode, said first valvebeing normally conducting and having its principal electrodes coupled tothe control electrode of said second valve in such relation that whensaid first valve is conducting it maintains said second valve in anon-conducting condition, a starting device actuable betweencircuit-closing and circuit-interrupting conditions, means responsive toactuation of said starting device from one said condition to the otherfor impressing a potential on the control electrode of said first valvewhich renders it non-conducting, means efiective after said first valveis rendered non-conducting for passing current between the principalelectrodes 4 of said second valve, and timing rneansoperably responsiveto said starting device for removing said potential from said controlelectrode of said first valve after the expiration of a predeterminedtime interval.

6. In a timing control system, first and second electric valves eachhaving principal electrodes and a control electrode, said first valvebeing normally conducting and having its principal electrodes coupled tothe control electrode of said second valve in such relation that whensaid first valve is conducting it maintains said second valve in anon-conducting condition, a starting device actuable betweencircuit-closing and circuit-interrupting conditions, means responsive toactuation of said starting device from one said condition to the otherfor impressing a potential on the control electrode of said first valvewhich renders it non-conducting, means effective after said first valveis rendered non-conducting for passing current between the principalelectrodes of said second valve, timing means operably re.-

sponsive-to said starting device and effective after the expiration of apredetermined period of conduction of said second valve to impress apotential on the control electrode thereof which prevents further suchconduction, and translating means disposed to be operated by the saidcurrent flowing through said second valve.

'7. In a timing control system, first and second electric valves eachhaving principal electrodes and a control electrode, said first valvebeing normally conducting and having its principal electrodes coupled tothe control electrode of said second valve in such relation that whensaid first valve is conducting it maintains said second valve in anon-conducting condition, a starting device actuable betweencircuit-closing and circuit-interrupting conditions, means responsive toactuation of said starting device from one of said conditions to theother for impressing a potential on the control electrode of said firstvalve which renders it non-conducting, means effective after said firstvalve is rendered non-conducting for passing current between theprincipal electrodes of said second valve, and timing means operablyresponsive to said starting device for removing said potential from saidcontrol electrode of said first value after the expiration of apredetermined time interval, said removal of said potential againrendering said first valve conductive and enabling it to prevent furtherconduction through said second valve.

8. In a timing control system, first and second electric valves, saidfirst valve having principal electrodes and a control electrode, saidfirst valve being normally conducting and having its principalelectrodes coupled to said second valve in such relation that when saidfirst valve is conducting it prevents flow of current through saidsecond valve, a starting device actuable between circuitclosing andcircuit-interrupting conditions, means responsive to actuation of saidstarting device from one said condition to the other for impressing apotential on'the control electrode of said first valve which renders itnon-conductive, means eiiective after said first valve is rendered nomconductive for passing current through said second valve, and meansoperated as a consequence of said actuation of said starting device forremoving said potential at the expiration of a controlled period.

9. In a timing control system, first and second electric valves, saidfirst valve having principal electrodes and a control electrode, saidfirst valve being normally conducting and having its principalelectrodes coupled to said second valve in such relation that when saidfirst valve is conducting it prevents flow of current through saidsecond valve, a starting device actuable between circuit-closing andcircuit-interrupting conditions, means responsive to actuation of saidstarting device from one of said conditions to the other for impressinga potential on the control electrode of said first valve which rendersit nonconductive, means effective after said first valve is renderednon-conductive for passing current through said second valve, and timingmeans controlled in accordance with the condition of said first valvefor removing the said potential irom said control electrode of saidfirst valve after the expiration of a predetermined time interval.

CLETUS J. COLLOM.

